Ryan Malloy
6dffd936ae
PlatformIO project for ESP32-S3 + SX1262 (Heltec WiFi LoRa 32 V3). Transmits periodic LoRa packets matching gr-lora_sdr receiver params: SF7, BW125kHz, CR4/5, 915MHz, sync word 0x12, CRC enabled. Verified end-to-end: beacon TX → RTL-SDR → Docker gr-lora_sdr → decoded "GR-MCP #N" payloads with valid CRC.
106 lines
2.9 KiB
C++
106 lines
2.9 KiB
C++
/*
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* Heltec V3 LoRa TX Beacon
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*
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* Transmits periodic LoRa packets for testing gr-mcp SDR reception.
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* Parameters match the gr-lora_sdr receiver defaults.
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*
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* Hardware: Heltec WiFi LoRa 32 V3 (ESP32-S3 + SX1262)
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*/
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#include <Arduino.h>
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#include <SPI.h>
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#include <RadioLib.h>
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// Heltec V3 SX1262 pin mapping
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#define LORA_NSS 8
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#define LORA_DIO1 14
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#define LORA_RST 12
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#define LORA_BUSY 13
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#define LORA_SCK 9
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#define LORA_MOSI 10
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#define LORA_MISO 11
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// Heltec V3 power control — Vext must be LOW to power LoRa + OLED
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#define VEXT_CTRL 36
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// Custom SPI bus for the LoRa radio (not the default Arduino SPI pins)
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SPIClass loraSPI(FSPI);
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// SX1262 with custom SPI
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SX1262 radio = new Module(LORA_NSS, LORA_DIO1, LORA_RST, LORA_BUSY, loraSPI);
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// LoRa parameters — must match gr-lora_sdr receiver
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const float FREQUENCY = 915.0; // MHz (US ISM band)
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const float BANDWIDTH = 125.0; // kHz
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const uint8_t SPREADING = 7; // SF7
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const uint8_t CODING_RATE = 5; // CR 4/5
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const uint8_t SYNC_WORD = 0x12; // LoRaWAN public sync word
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const int8_t TX_POWER = 14; // dBm
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const uint16_t PREAMBLE_LEN = 8; // symbols
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uint32_t packet_count = 0;
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void setup() {
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Serial.begin(115200);
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delay(2000); // wait for USB CDC enumeration
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// Enable Vext to power the LoRa radio
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pinMode(VEXT_CTRL, OUTPUT);
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digitalWrite(VEXT_CTRL, LOW);
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delay(100);
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Serial.println("=== Heltec V3 LoRa TX Beacon ===");
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Serial.printf("Freq: %.1f MHz, SF%d, BW%.0fk, CR4/%d\n",
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FREQUENCY, SPREADING, BANDWIDTH, CODING_RATE);
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Serial.printf("Sync: 0x%02X, Power: %d dBm\n", SYNC_WORD, TX_POWER);
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// Initialize custom SPI bus with Heltec V3 LoRa pins
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loraSPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_NSS);
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Serial.println("SPI initialized on SCK=9 MISO=11 MOSI=10 NSS=8");
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int state = radio.begin(
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FREQUENCY,
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BANDWIDTH,
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SPREADING,
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CODING_RATE,
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SYNC_WORD,
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TX_POWER,
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PREAMBLE_LEN
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);
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if (state != RADIOLIB_ERR_NONE) {
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Serial.printf("Radio init FAILED: %d\n", state);
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while (true) { delay(1000); }
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}
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// SX1262-specific: set DIO2 as RF switch control (required for Heltec V3)
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radio.setDio2AsRfSwitch(true);
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// Use explicit header mode (default for LoRa)
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radio.explicitHeader();
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// Enable CRC (gr-lora_sdr expects CRC)
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radio.setCRC(true);
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Serial.println("Radio initialized OK, starting TX loop");
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}
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void loop() {
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char payload[64];
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snprintf(payload, sizeof(payload), "GR-MCP #%lu", (unsigned long)packet_count);
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Serial.printf("[TX %lu] \"%s\" ... ", (unsigned long)packet_count, payload);
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int state = radio.transmit((uint8_t*)payload, strlen(payload));
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if (state == RADIOLIB_ERR_NONE) {
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Serial.printf("OK (%d dBm)\n", TX_POWER);
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} else {
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Serial.printf("FAIL: %d\n", state);
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}
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packet_count++;
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delay(3000); // TX every 3 seconds
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}
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